1. Field of the Invention
The present invention relates to a data communication transponder, such as a radio-wave tag or IC card, and a communications system employing such a transponder, and in particular to a data communication transponder having a plurality of data storage areas for use in communicating with interrogators of a plurality of providers and a communications system employing such a transponder.
2. Description of the Prior Art
Nowadays, communications systems are known that permit a single IC card, used as a transponder, to communicate with a plurality of types of reader/writer (interrogator) managed individually by a number of providers. To realize such a communications system, an IC card employed therein has memory divided into a plurality of memory areas allocated individually to a number of providers in order to achieve separate storage of data in communicating with the reader/writers managed individually by those providers. In this system, where a single IC card can communicate with reader/writers managed individually by a number of providers, it is essential, during communication, to permit the use of only a particular memory area allocated to the provider that manages the reader/writer with which a given IC card is currently communicating and simultaneously prohibit the use of the other memory areas.
To achieve this, each IC card has a plurality of cipher keys stored therein that permit the individual memory areas to be used only when communicating with the reader/writers managed by the corresponding providers to which those memory areas are allocated. An IC card and a reader/writer authenticate each other by the use of such a cipher key. A non-contact communications system involving such a mutual authentication process is proposed in Japanese Laid-Open Patent Application No. H10-327142.
In the communications system proposed in Japanese Laid-Open Patent Application No. H10-327142 mentioned above, as shown in FIG. 11, the cipher keys that are used to permit the use of the individual memory areas secured within an IC card are determined provider by provider. Moreover, once a particular provider is authenticated by the use of the corresponding cipher key, the IC card can recognize, on the basis of the same cipher key, which memory area the provider will request access to. On the other hand, a reader/writer can check whether a given IC card is authentic or not, but cannot identify it (i.e. cannot distinguish one IC card from another). Therefore, to permit reader/writers to identify IC cards, each IC card has also an ID (identification) number unique thereto stored therein.
However, in this system, the cipher keys that are used to permit the use of the memory areas secured within an IC card are determined provider by provider as described above, and thus those cipher keys are not unique to the IC card. Moreover, the ID number stored in an IC card is issued when the IC card is manufactured, and therefore the ID number, at the same time as it is stored in the IC card, needs to be registered also in individual providers. Thus, every time an IC card is manufactured, its ID number needs to be registered in individual providers. This complicates the management of the communications system.
An object of the present invention is to provide a data communication transponder and a communications system employing such a transponder that offer higher security by permitting cipher keys, used to permit the use of memory areas secured within an IC card, to be so determined as to be unique to the IC card.
To achieve the above object, according to one aspect of the present invention, a transponder for data communication is provided with: a plurality of storage areas for storing data used when the transponder communicates individually with a plurality of interrogators managed by different parties; a plurality of key signals, unique to the transponder and stored one for each of the storage areas, for permitting the use of only a particular storage area corresponding to the interrogator with which the transponder is currently communicating. Here, the transponder, when communicating with an interrogator, checks the key signal received from the interrogator against the key signals stored in the transponder and, when the received key signal coincides with one of the stored key signals, the transponder is permitted to communicate with the interrogator by using only a particular storage area corresponding to that interrogator.
In this transponder for data communication, the providers that manage the interrogators that can communicate with the transponder determine the cipher keys, which are used when the transponder communicates with the interrogators, in such a way that those cipher keys are unique to the transponder. When the transponder, having the cipher keys determined in this way, attempts to communicate with one of the interrogators, the interrogator can identify the transponder.
According to another aspect of the present invention, a non-contact communications system is provided with: a plurality of interrogators that are managed by different parties; and a transponder for data communication having a plurality of storage areas for storing data used when the transponder communicates individually with the interrogators and a plurality of key signals, unique to the transponder and stored one for each of the storage areas, for permitting the use of only a particular storage area corresponding to the interrogator with which the transponder is currently communicating. Here, the transponder, when communicating with an interrogator on a non-contact basis, checks the key signal received from the interrogator against the key signals stored in the transponder and, when the received key signal coincides with one of the stored key signals, the transponder is permitted to communicate with the interrogator by using only a particular storage area corresponding to that interrogator.
In this communications system, the providers that manage the interrogators that can communicate with the transponder determine the cipher keys, which are used when the transponder communicates with the interrogators, in such a way that those cipher keys are unique to the transponder. When the transponder, having the cipher keys determined in this way, attempts to communicate with one of the interrogators, the interrogator can identify the transponder.